You want ForcedInduction to explain boost phenomena, not me.

Evan, the ball and spring go into the T-fitting followed by the set screw. The set screw preloads the spring. The ball plus spring pressure blocks air coming from the left fitting from getting to the bottom fitting. As the boost signal increases, it eventually overcomes the spring and pushes the back back allowing pressurized air to the bottom fitting which leads to the wastegate. There should be a bleed hole (visible in the picture in the initial post) to relieve pressure in the actuator when the ball closes. Otherwise the wastegate might get stuck partially open or take a long time to close. Yes, there is a bit of boost bleed through the relief hole but only when the boost signal is going through.

Sixto
87 300D